1. Field
Apparatuses and methods consistent with exemplary embodiments relate to an image processing apparatus of restoring images through frequency decomposition and compounding, a control method of the image processing apparatus, and an ultrasound imaging apparatus, and more particularly to, a technique for determining one or more frequency bands of an ultrasound image signal through analysis of speckle energy of the ultrasound image signal, acquiring adaptive multi-frequency images according to images or depths through frequency decomposition, and performing frequency compounding and axial restoration, to prevent axial resolution degradation.
2. Description of the Related Art
An ultrasound imaging apparatus is widely used for medical purposes such as, for example, observing the inside of an object, detecting foreign materials from the object, and examining an injury, by irradiating ultrasonic waves generated from transducers of a probe toward a target inside the object from the surface of the object, and receiving information of ultrasonic signals (that is, ultrasonic echo signals) reflected from the target so as to non-invasively acquire section images about soft tissue of the object or images about blood vessels of the object based on the ultrasonic echo signals.
The ultrasonic imaging apparatus has advantages in that the ultrasonic imaging apparatus is a compact, low-priced apparatus compared to other medical imaging apparatuses, such an X-ray imaging apparatus, a computed tomography (CT) scanner, a magnetic resonance image (MRI) apparatus, and a nuclear medicine diagnosis apparatus, and the ultrasonic imaging apparatus can display images in real time. Also, the ultrasonic imaging apparatus has high safety since there is no risk for patients to be exposed to radiation. For the advantages, the ultrasonic imaging apparatus is widely used.
Lately, according to the wide use of ultrasound system, requirements for ultrasound images that are provided by the ultrasound system are increasing. Particularly, since a patient's lesions or tissue needs to be accurately observed for examination, a biopsy, or a surgery, the ultrasound system needs to acquire accurate ultrasound images.
The ultrasound imaging apparatus uses a probe which is an ultrasonic wave generator in order to acquire an ultrasound image of an object. The probe includes one or more transducers such that the individual transducers transmit ultrasonic waves to an object, and receive echo ultrasonic waves from the object. In order to compensate for the differences between times of arrival of ultrasonic waves at the transducers, beamforming is performed. The ultrasound imaging apparatus acquires an ultrasound image of the object based on the beamformed signals.
In order to improve a contrast to noise ratio (CNR) of an ultrasound image, a frequency compounding method is widely used. According to the frequency compounding method, when the ultrasound imaging system extracts frequency bands in a frequency domain using beamformed images to acquire a plurality of images for the individual frequency bands, axial resolution may be degraded upon compounding of the images of narrow bands since the images have different speckle patterns due to the differences between frequency areas.
Thus, a technique for removing speckle noise caused by compounding of ultrasound images and improving resolution by analyzing speckle energy of input images is needed.